The American legal system, as well as some other legal systems around the world, relies heavily on written judicial opinions—the written pronouncements of judges—to articulate or interpret the laws governing resolution of disputes. Each judicial opinion is not only important to resolving a particular legal dispute, but also to resolving similar disputes, or cases, in the future. Because of this, judges and lawyers within our legal system are continually researching an ever-expanding body of past opinions, or case law, for the ones most relevant to resolution of new disputes.
To facilitate these searches, companies, such as West Publishing Company of St. Paul, Minn. (doing business as West Group), collect and publish the judicial opinions of courts across the United States in both paper and electronic forms. Many of these opinions are published with bibliographic cites or hyperlinks to historically related opinions, known as prior cases, from other courts that have previously ruled on all or part of the same dispute. The cites and hyperlinks enable researchers to find printed volumes containing the related opinions or readily access the related opinions electronically over a computer network. For example, an opinion in a patent case from the United States Supreme Court, the highest court in the United States, would generally cite not only an opinion from the Court of Appeals for the Federal Circuit, the next highest court for patent cases, but also an opinion of a local Federal District Court where the patent case started, thus documenting the history or progression of the case through the U.S. federal judicial system.
Although it may seem a simple matter to identify the prior cases for any given case, the reality is that identifying these cases is problematic for at least three reasons. First, the vast majority of opinions (about 90%) as originally written do not explicitly identify their prior cases, in part because some prior cases are only published after the opinions that should cite them were published. Second, there are no straightforward rules based on the court titles to determine even when to look for prior cases, since appellate courts—courts that review the decisions of other courts—sometimes hear new cases, and trial courts—courts that hear new cases—sometimes re-decide old cases that have been remanded (sent back) from appellate courts. And third, even when one knows to look for a prior case, the conventional technique of computer-based text-matching (that is, searching existing opinions for those with court dockets, case title, and party names that match those in a given case) not only suggests too many non-prior cases, but also misses too many actual prior cases, creating additional work for human reviewers without necessarily improving accuracy.
Accordingly, the present inventors have recognized a need for new tools and methods to facilitate identification of historically related cases, and potentially other types of related documents.